THE SKULL. 53 
mandible. This fossa is bounded caudally by the prominent 
postmandibular process (7). 
All that portion of the lateral surface of the skull which lies 
craniodorsad of the lambdoidal ridge may be divided (exclud- 
ing the zygomatic arch) into three main parts, the temporal 
fossa, the orbital fossa, and the face. The boundaries of the 
temporal fossa have been given. The orbital fossa is bounded 
Fic. 40.—SKULL, SIDE VIEW. 
1, occipital bone; 2, interparietal; 3, parietal; 4, temporal; 5, 5’, frontal; 6, 
malar; 7, sphenoid; 8, palatine; 9, presphenoid; 10, maxillary; 11, nasal; 12, pre- 
maxillary; 13, incisor teeth; 14, canine; 15, 16, 17, premolars; 18, molar. a, oc- 
cipital condyle; 4, external occipital crest; c, sagittal crest; ¢, lambdoidal ridge; e, 
tympanic bulla; 7, jugular process; g, mastoid process; 2, stylo-mastoid foramen; 3, 
pit for tympanohyal bone; 7, external auditory meatus; 2, zygomatic process of tem- 
poral bone; 7, mandibular fossa; m, postmandibular process; #, zygomatic process 
of the frontal; 0, supraorbital margin; 7, external pterygoid fossa; g, sphenopalatine 
foramen; 7, orbital fissure; s, internal pterygoid fossa; z, hamulus; #, foramen 
ovale; v, foramen rotundum; w, optic foramen; +, opening of lachrymal canal; y, 
infraorbital foramen, 
externally by a prominent semicircular ridge formed chiefly by 
the zygomatic arch, the zygomatic process of the frontal (z), 
’ and the supraorbital arch (0) of the frontal, which may be 
traced to the cranial root of the zygomatic arch. The orbital 
fossa may be considered to end caudally and ventrally at the 
level of the optic foramen (z); ventrad of it are certain smaller 
fosse. Immediately ventrad is the long external pterygoid 
fossa (/), from which arises part of the external pterygoid 
muscle. This fossa begins at the sphenopalatine foramen (¢) 
and extends caudad to the orbital fissure (7); it is separated 
by a ridge from the orbital fossa. Caudoventrad of the external 
